1. Field of the Invention
The present invention relates to a method of fabricating a thin,film transistor used in a display apparatus such as a liquid-crystal display apparatus, and to a liquid-crystal display apparatus having TFTs fabricated using the method.
2. Description of the Related Art
The recent trend for display apparatus such as liquid-crystal display apparatus has been toward larger screen area and higher resolution. This trend has involved producing a larger-area glass substrate while making thin-film transistors (hereinafter referred to TFTs) even smaller. To fabricate TFTs on a low-cost, large-area glass substrate, low-temperature processing at 400.degree. C. or lower is preferable. Currently, TFTs for this purpose are fabricated using thin films of amorphous silicon (a-Si) that can make thin films with good uniformity relatively easily at low temperatures. In the fabrication of such an a-Si TFT, the following two methods are known for forming source and drain regions: in one method, a SiH.sub.4 gas containing an impurity gas such as a PH.sub.3 gas is decomposed by discharge to deposit an n.sup.+ a-Si film, thereby forming the source and drain regions; in the other method, a gas containing impurities such as a hydrogen diluted PH.sub.3 gas is ionized by discharge, and the resulting ions are accelerated and implanted into the a-Si film without mass separation, to form a doped film such as an n.sup.+ a-Si film, thereby forming the source and drain regions. This method is referred to as an ion shower doping method and explained in, for example, Japanese Patent Laid-Open Publication Nos. 63-194326, 4-39967, 5-243270, and 6-37110.
However, the resistivity of the source and drain regions (n.sup.+ a-Si film) formed by the above two conventional methods is as high as 10.sup.3 .OMEGA..multidot.cm, which leads to degradation of transistor characteristics.
The present invention overcomes the aforementioned problems associated with the conventional methods, and provides a method of fabricating a TFT having source and drain regions of a low resistance, and also provides a liquid-crystal display apparatus that uses such TFTs in its display panel and that can provide a larger-area, higher-resolution screen.